The Chhattisgarh government on Wednesday sounded alert for several districts as well as neighbouring Orissa in the wake of overflowing of Pandit Ravi Shankar Dam in Dhamtar district following heavy rainfall, as the weather bureau predicted no respite from rain in the next 24 hours.

The water level in the dam on river Mahanadi at Gangrel has crossed its danger mark by 30 cm and touched 349 metre, Gangrel Dam Authority sources told PTI over phone from Dhamtari, about 70 km from Raipur.

All 14 gates of the dam have been opened, they added.

At present the water inflow into the reservoir was 1.46 lakh cusecs whereas the outflow was about one lakh cusec, they said, adding that more water needed to be released to bring the water level below the danger mark.

In Orissa's coastal deltaic plains, the Mahanadi, which is the state's biggest river system, threatened to inundate large areas in at least seven districts.

"We are expecting a massive sheet of water to flow down the river following heavy rainfall in the lower catchment region of the river," Special Relief Commissioner Jagadananada Panda told PTI in Bhubaneswar.

Collectors of the districts threatened with inundation have been alerted and all measures are being taken to tackle the possible situation, he said.

The Mahanadi, downstream of the huge Hirakud dam near Sambalpur, is mainly fed by the Tel river, the catchment of which had experienced heavy rainfall during the last 24 hours.